1. Field of the Invention
This invention relates to a transfer apparatus, a recording control apparatus, a transfer method and a recording control method for an information signal such as, for example, an audio signal or a video signal.
2. Description of the Related Art
As digital contents are popularized, infringement upon copyright by illegal copying of digital contents becomes an issue. In particular, since analog recording onto a tape medium or a like medium records audio data or video data in an analog fashion, copying of data deteriorates the quality of the data. In contrast, apparatus which record and reproduce audio data or video data in a digital fashion do not give rise to a problem of deterioration of the information quality by copying in principle and allows a large number of times of copying of information to be performed without any deterioration of the information quality.
Consequently, the damage by illegal copying by means of an apparatus which processes information digitally is much greater than that by means of an apparatus which processes information in an analog fashion. Therefore, it is very significant to prevent illegal copying by an apparatus which processes data in a digital fashion.
As a countermeasure to this problem, information for copy control is added to digital contents so that illegal copying may be prevented using the additional information.
For example, as a control for prevention of copying, a copyright protection measure according to a generation limiting copying control system called SCMS (Serial Copy Management System) wherein copying of audio contents is permitted once but further copying from the copy is inhibited is employed by a CD (Compact Disc), an MD (Mini Disc; trademark), a DAT (Digital Audio Tape) or a like medium.
A copying control system of the SCMS is described below with reference to FIG. 1.
For example, an audio signal of an original source is recorded digitally on a disc 1. The digital audio signal is recorded in a predetermined recording format on the disc 1; and additional information representing that copying is permitted only once according to the SCMS system is recorded, for example, in a particular area in the digital signal.
A reproduction apparatus 2 reads out a signal from the disc 1, reproduces the digital audio signal from the read signal and transmits the reproduced audio signal to a recording apparatus 3 together with the additional information. Thereupon, the reproduction apparatus 2 transmits the digital audio signal to the recording apparatus 3 in a time equal to the time required for reproduction of the digital audio signal at a normal reproduction rate (normal or standard rate).
The recording apparatus 3 receives the digital audio signal and, if the additional information to the digital audio signal indicates that copying is permitted once, recognizes that copying of the input digital signal is possible. Thus, after the recording apparatus 3 confirms that the additional information indicates that copying is permitted once, it records the digital signal as a copy onto a recordable disc 4. Thereupon, the recording apparatus 3 rewrites the additional information from “copying is permitted once” to “copying is inhibited”. Accordingly, copying recording of the digital recording is performed onto the recordable disc 4, and the information of “copying is inhibited” is recorded as the additional information to the digital signal.
When the disc 4 (disc of the first generation) for which copying recording has been performed for the first time is reproduced by a reproduction apparatus 5 and the digital signal thus reproduced is supplied to a recording apparatus 6, the recording apparatus 6 recognizes that the additional information indicates that copying is inhibited, and therefore cannot record the digital signal onto a recordable disc 7.
The copying rate then is equal to the transmission rate of the audio signal from the reproduction apparatus 2 and is equal to a normal reproduction rate at which the audio signal is reproduced in a standard reproduction time.
As described above, the SCMS system achieves protection of the copyright by controlling so that, although copying of the first generation is permitted, copying of the second generation from a medium of the first generation is inhibited.
The copyright protection by the SCMS system, however, has a problem in that, although copying of the second generation is inhibited, copying of the first generation from one original source is permitted any number of times to produce copies. In the conventional copying control system described above, since the time required for copying is equal to the standard reproduction time, time is required for copying, and it has been considered that actual damage to copyright protection is not very significant.
However, according to digital recording onto a disc or a semiconductor memory in recent years, high rate copying can be performed readily when compared with conventional copying onto a tape by analog recording. Particularly where a signal compression technique is used for an audio signal or where an audio signal is transferred at a high bit rate, copying also at a multiple rate is possible.
Where such high rate copying as just described is allowed, copying of the first generation can be performed in a very short time, and this makes it possible to produce a large number of copies of the first generation in a short time from one original source. Consequently, there is a possibility that copyright protection may not be achieved effectively. Therefore, taking such a variation in technical environment regarding copying as described above into consideration, it is demanded to introduce a copyright protection system which limits copying more strictly than ever.
To an owner of copyright, it is advantageous to introduce a system which strictly limits copying in this manner. However, to a user, the system is not acceptable because copying which has been permitted till now is inhibited.
Therefore, if a new copyright protection system which strictly limits copying is adopted by a recording apparatus to be placed on the market newly, since copying by a conventional recording apparatus makes a loophole to illegal utilization, the recording apparatus which adopts the new copyright protection system may not possibly be accepted by the market.